1. Field of the Invention
The present invention relates to patient monitoring. Although embodiments make specific reference to monitoring impedance and electrocardiogram signals with an adherent patch, the system methods and device described herein may be applicable to many applications in which physiological monitoring is used, for example wireless physiological monitoring for extended periods.
Patients are often treated for diseases and/or conditions associated with a compromised status of the patient, for example a compromised physiologic status. In some instances, a patient may report symptoms that require diagnosis to determine the underlying cause. For example, a patient may report fainting or dizziness that requires diagnosis, in which long term monitoring of the patient can provide useful information as to the physiologic status of the patient. In some instances a patient may have suffered a heart attack and require care and/or monitoring after release from the hospital. One example of a device to provide long term monitoring of a patient is the Holter monitor, or ambulatory electrocardiography device.
In addition to measuring heart signals with electrocardiograms, known physiologic measurements include impedance measurements. For example, transthoracic impedance measurements can be used to measure hydration and respiration. Although transthoracic measurements can be useful, such measurements may use electrodes that are positioned across the midline of the patient, and may be somewhat uncomfortable and/or cumbersome for the patient to wear.
Work in relation to embodiments of the present invention suggests that known methods and apparatus for long term monitoring of patients, for example in-home monitoring, may be less than ideal. At least some of the known devices may not collect the right kinds of data to treat patients optimally. For example, although successful at detecting and storing electrocardiogram signals, devices such as the Holter monitor can be somewhat bulky and may not collect all of the kinds of data that would be ideal to diagnose and/or treat a patient. In at least some instances, devices that are worn by the patient may be somewhat larger than ideal and may be uncomfortable, which may lead to patients not wearing the devices and not complying with directions from the health care provider, such that data collected may be less than ideal. Further, in at least some instances the current devices may have less than ideal performance when the patient resumes a normal lifestyle and the device is exposed to environmental factors such as humidity or water, for example, when the patient takes a shower. Although implantable devices may be used in some instances, many of these devices can be invasive and/or costly, and may suffer at least some of the shortcomings of known wearable devices.
Current methodologies for measuring patient hydration with impedance may be less than ideal for remote patient monitoring, such as in-home monitoring for extended periods. At least some of the current devices that determine hydration with impedance, for example for hospital use, may use more current and may have more complex and bulky circuitry than would be ideal for in-home monitoring in at least some instances, for example where the patient is active and moves about the home. As noted above, the size and comfort of a remote patient monitor can affect the quality of the data received from the patient.
Therefore, a need exists for improved patient monitoring, for example improved in-home patient monitoring. Ideally, such improved patient monitoring would avoid at least some of the short-comings of the present methods and devices.
2. Description of the Background Art
The following patents and publications may describe background art relevant to the present application: U.S. Pat. No. 7,133,716 to Kraemer et al.; U.S. Pat. No. 6,906,530 to Geisel; U.S. Pat. No. 6,442,422 to Duckert; U.S. Pat. No. 6,050,267 to Nardella et al.; U.S. Pat. No. 5,935,079 to Swanson et al.; U.S. Pat. No. 5,836,990 to Li; U.S. Pat. No. 5,788,643 to Feldman; U.S. Pat. No. 5,738,107 to Martinsen et al.; U.S. Pat. No. 5,449,000 to Libke et al.; U.S. Pat. No. 4,966,158 to Honma et al.; U.S. Pat. No. 4,692,685 to Blaze; U.S. Patent App. Pub. No. 2007/0043301 to Martinsen et al.; U.S. Patent App. Pub. No. 2006/0281981 to Jang et al.; U.S. Patent App. Pub. No. 2006/0004300 to Kennedy; U.S. Patent App. Pub. No. 2005/0203435 to Nakada; and U.S. Patent App. Pub. No. 2005/0192488 to Bryenton et al.